Resolution of hetebocyclic nitro



Patented May 13, 1947 RESOLUTION OF HETEROCYCLIC NITRO- GEN BASEIVIIXTURES Karl Henry Engel, West Englewood, N. J., as-

signor to Allied Chemical & Dye Corporation, New York, N. Y., acorporation of New York No Drawing. Application August 26, 1942, SerialNo. 456,257

This invention relates to the resolution of mixtures of S-picoline,l-picoline and 2,6-lutidine, particularly to the separation ofB-picoline from said mixtures.

The picolines and other homologs of pyridine are customarily extractedalong with other nitrogen bases from coke oven distillates and othersources of heterocyclic nitrogen bases by means of an aqueous solutionof mineral acid, usually sulfuric acid. After liberation from these acidsolutions by means of alkali, the base mixtures thus obtained arecustomarily fractionally distilled to obtain fractions predominating ina particular base. Bases such as pyridine, boiling point 116 0., and2-picoline, boiling point 129.4 C., can generally be obtained inreasonably pure form by fractional distillation, but for the most partthe remaining compounds cannot be separated by ordinary distillationmethods alone. In-' stead, the fractions obtained, even when they are ofrelatively narrow boiling range, contain increasing numbers of pyridinehomologs and their isomers. Mixtures of this kind have found limitedpractical application, mainly as special solvents, and are of relativelylow economic value. The individual bases in pure form, however, areproducts of considerable commercial interest, being useful, for example,in the preparation of pharmaceutical products and dyes. The purityrequirements in these fields are quite rigid.

3-picoline, which is found in fractions boiling predominantly within therange 140-145 C., is of especially high potential value. Nicotinic acid,for example, a member of the vitamin B complex, may be obtained byoxidation of B-picoline. When mixtures of heterocyclic nitrogencompounds are recovered from sources such as coal tar, the fractionstaken within the range 140- 145 0., even closely cut fractions withinthis boiling range, in general contain as components three pyridinehomologs of substantially the same boiling point in roughly equalproportions; i. e., 2,6-lutidine, boiling point 143.8 C., 3-picoline(beta-picoline), boiling point 143.8 C., and 4- picoline(gamma-picoline) boiling point 144.8" C. Derivatives of these compoundsare becoming of increasingly greater importance as pharmaceuticals andagricultural chemicals.

Since the three components making up the usual nitrogen base fractionsboiling within the range l40-145 C. (2,6-lutidine, 3-picoline, and4-picoline) have substantially the same boiling points, fractionaldistillation is obviously unsatisfactory as a means for resolving themixtures. Other methods of resolving such mixtures here- 11 Claims. (Cl.260290) tofore disclosed in the published prior art have been generallyunsatisfactory in regard to production yields and production costs. Suchother methods have usually depended upon fractional crystallization ofthe more common salts of the bases present, e. g., the sulfates,oxalates, chlorates, picrates, ferro-cyanides and the like. Isolation orpurification of individual bases by such methods has been found to beextremely cumbersome and generally insufiiciently sharp to obtaincompounds of .a purity demanded in industry. These methods also haveoften presented other drawbacks such as prohibitive cost, explosionhazards, and toxicity.

It is an object of this invention to provide a commercially feasibleprocess for resolving nitrotions, particularly tar base fractionsboiling in i the range l40--145 C. containing these constituents inroughly equal proportions.

It is a further object of this invention to provide a process forseparating substantially pure 3-picoline or B-picoline-enrichedfractions from mixtures thereof with closely related nitrogen bases suchas 2,6-1utidine and 4-picoline not readily separable therefrom bydistillation.

I have discovered that substantially pure 3- picoline or3-picoline-enriched fractions may be recovered in substantial proportionfrom mixtures containing 3-picoline, 4-pico1ine, and 2,6- luti'dine byprecipitating all or the major part of the 2,6-lutidine and 4-picolinefrom such mixtures in the form of their hydrochlorides. I have foundthat the hydrochlorides of 2,6-luti'dine and.

4-picoline are substantially insoluble in the 3- picoline with whichthey are associated in close boiling fractions, and are alsosubstantially insoluble in hydrocarbon solvents of the aromatic,naphthenic, or aliphatic ty es. My invention also comprises a process inwhich a tar base mixture is first fractionated to obtain a fractionboiling predominantly in the range l40-145 0. containing substantialproportions of 2,6-lutidine, 3- picoline and -picoline, and the bulk ofthe 2,6- lutidine and 4-picoline is then separated from this fraction inthe form of their hydrochlorides.

In the process of my invention, the bulk of the 2,6-lutidine and-picoline may be precipitated in one step as a hydrochloride mixture,leaving the 3-picoline, or, alternatively, the 2,6-lutidine and4-picoline may be precipitated in successive steps in the form of theirhydrochlorides. Thus I have found that 2,6-lutidine hydrochloride isprecipitated preferentially with respect to eitherof the 3 picolinehydrochlori'des, and 4-piccline hydrochloride is then precipitatedpreferentially with respect to 3-picoline hydrochloride.

In a preferred method of carrying out the process of my invention, acommercial picolinelutidine fraction, suitably a tar base fractionboiling pre'dominantly'within the range of 140- 145 C. and containingroughly equal proportions of 3-picoline, 4-picoline, and 2,6-lutidine,may be treated with gaseous hydrogenchloride, for'ex ample the hydrogenchloride gas obtainedicommercially from the reaction ofsodium chloridewith sodium bisulfate or as a b'y-p'roductin the commercial chlorinationof h-yd r-oca .rbons such as benzene. This hydrogen chloride gas may beadded to the three-component'mixtureof bases or to solutions of thebases in a solvent such-as benzene, toluene or parafiinic hydrocarbons:Heat evolved in the ensuing reaction between bases and hydrogen chlorideis removed by external cooling. Instead of gaseous hydrogen chloride,the base mixture may alternatively be treated with an aqueoushydrochloric acid which may advantageously be the inexpensive andreadily available technical grade of muriatic acid. The term hydrogenchloride is used herein -to' includeboth gaseous hydrogen chloridean'dhydrochlor-ic acid. This treatment maybe carried out without anydiluent present, but is preferably carried'out in .thepre'sence eitherof 3picoline concentrate from a previous run or an inexpensivehydrocarbon solvent such as benzene, toluene, or a parafi inicor'naphthenic petroleum solvent.

An amount of hydrogen chloride exactly sufficient to react with the2,6'-lutidine .and .4'-picoline may be employed; A mixed precipitate of2,'6-1utidine hydrochloride and 4-pi'coline hydrochloride is thusobtained. However, the precipitation of these hydrochlorides may. becarried out in two stages, in the first of which a little less hydrogenchloride than the molar equivalent of' 2,6-li1tidine present in themixture is employed. In this case especially'pure 2I6 l utidinehydrochloride is precipitatedin .the first stage and may besep'arated'b'y filtration. 2,6-lutidine of substantially 10.0% purityhas thus been obtained. Application, of additional hydrogen chloridethereafter in a second stage in amount equivalent to the l-picoline and2B- liit'i dine remaining in the base mixture leads to precipitation ofa 'mixture-of'base hyd'rochlorides in which 4-picoline hydrochloridegreatly predominates, concentrations of Y85 %,9f0% being obtainable. Afixed small ratio of 2,6-lutidine is simultaneously precipitated, itsconcentration in the liberated bases from the second hydrochlorideprecipitate being'about 4%. By proper limitation of hydrogen chloride,precipitation of' 3- pic'oline can beavoidedl The reaction of the baseswithhydrogen chlo-- ride may be carried-out at whatevertemperature isconveniente. g., the normally prevailing temperature. When an aqueoushydrochloric acid is employed; the mixture is heated to refluxingtmperaturaprefrably in the presence ofa diluent such as 3 -picolineconcentrate frorna previousrun to remove the water by azeotrop icdistillation. The distillate is condensed in a side arm trap where itseparates into a Water layer and an oil layer. The water layer isremoved while'the oil layercontaining' unreajcted base and diluent,Where such has been used, is continuously'returned't'o'the still. Whenall, or nearly all, of the water has thus'been removed, the'st'ill 4charge is cooled to normally prevailing temperatures to bring about orcomplete crystallization of the hydrochloride.

The precipitated crystals are isolated by filtration, e, g., bycentrifuging, and are freed from adhering 3-picoline mother liquor byWashing with a hydrocarbon solvent, e. g., the same hydrocarbon used asdiluent for the precipitation. The crystals may be freed from theadhering sol- .vent by dryingor other means. Depending upon whether thehydrochloride precipitation wa carried out in one step or two steps,either a mixed 2,6-lutidine hydrochloride and 4-picoline hydrochlorideproduct or separate products such as pure 2,6 lutidine hydrochloride anda fraction greatlyenri'ched in 4-picoline hydrochloride arethusobtained. In either case, the nitrogen base is liberated from thecrystals thus obtained, for example by adding an equivalent weight ofalkali toan aqueous solution of the basehydrochloride. Theliberatedb'aseWhich separates out from the resulting salt solution is dehydrated (forexample, bytre'ating with solid caustic soda) and distilled.

The mother and wash liquors may be distilled to recover solvent forreuse'in' thepr'ocess, andt'o recover the residual 3-pi'c'oline ;concentrafte. Where the precipitation is carried out with a carefullycontrolled amount of hydrogen chloride as 'above'irrdic'a'te'd; andequilibrium conditions at ordinary temperatures are approached, themother'liquorwill'have ap roximately the following composition: 3-picolinle, 86%, lI-picoline, 10%, and 2,'6-lut'idine', .4%. In actualoperation, a 3-pic oline" concentrate containing from 75%- 86%3-picoline may be obtained. Other heterocyclic bases which may have beenpresent in small amounts in the original base mixture, suchas2'-picolin'e an'd'ZA-lutidine, also remain in the 3-pi colin'econcentrate. This concentrate has a sufiiciently highI3'-picol ine.content so that it may be utilized'as such in the production ofderivatives, such as oxidation to. nicoti'nic'acid. If pure 3-pic'o'lineis desired, however, it may be ob.- tained in excellent yields byprecipitation as phosphate from an alcoholic'solution, in accordancewith the'proce'ss of my copending application Serial No. 346,347, filedJuly 19, 1940.

Where the production of a-3-pic'olin'e concentrate isjthemoreimportantlobject of the process, precipitation of the 2,6-lut'idineand l picol'ine hydrochlorides is preferablycarriedout as aboved'escribedin a single operation. In such a case, the mass of precipitatemay bje disproportionately b lky in relation to the quantity of motherliquor, and'the use of a diluent such as a hydrocarbon solvent of.coaltar or'pet'roleum origin is particularly advantageous. The handlingof a bulky precipitate'lnay'alsobe avoided by car-rying outtheprecipit'ationof hydrochloride in-a plurality of stages. When theproduction of pure 2;,6i-lutidine is not important, the amount ofhydrogen chloride added in the preliminary stages in multi-st'ageprecipitation is a matter of convenience. In the final stage, however,an amount of h o e chloride h l b adde such that the total hydrogenchloride used" is equivalent as accurately as this can be calculated tothe Zfi eIutidine' and 4-pic'oline in the base mixture.

Where the precipitation vof'the hydrochlorides occurs from ahot-solution, as in the above process where hydrochloric acid'is usedfor the precipijtatioh and the reaction mixture is refluxedtoremovewater, I have'found it is preferable to avoidor hold to aminimum theuse of hydrocarbon oils as diluents, at least in the initialcrystallization stages, since the base hydrochlorides in precipitatingfrom a hot hydrocarbon solution tend to form undesirably large masses,lumps,- or pebbles of solids while the crystals which form in hot3-picoline mother liquor alone are small and granular and easilyhandled. Preferably, therefore, 3-picoline concentrate from a precedingrun is used as diluent, at least in the initial stages of precipitationwhere the precipitation occurs in a hot solution. After precipitation iscomplete or is well along, however, hydrocarbon diluents may be addedfor ease in handling a bulky precipitate.

I have found it is desirable, when using hydrochloric acid for theprecipitation, to dehydrate the charge as thoroughly as possible, asmall residual percentage of moisture altering the solubilitycharacteristics of the hydrochlorides which it is desired toprecipitate, particularly the l-picoline hydrochloride. A moisturecontent greater than about 1.5% in the mother liquor is undesirable. Ihave also found it is undesirable, for the same reason, to have anappreciable amount of a lower alcohol, such as ethanol or methanol,present in the reaction mixture.

The process of my invention may advantageously be applied in theresolution of heterocyclic nitrogen compound mixtures obtained from cokeoven distillates, cracked petroleum, shale tar, bone oils, and fromother natural as well as synthetic sources of these base mixturescontaining substantial amounts of 3-pico1ine and other nitrogen basesnot readily separable therefrom by distillation, e. g., 4-picoline and2,6.-lutidine. As above pointed out, in carrying out the process of myinvention, such a mixture is advantageously first subjected tofractional distillation whereby a close out fraction containingpredominantly the 3-piaoline and other close boiling compounds isobtained.

7 The following examples are illustrative of the process of myinvention:

Example 1.-Resolution of a 2,6-lutz'dz'ne-3- picoline-l-m'colinefraction involving isolation of pure 2,6-lutz'dzne The apparatus usedconsisted of an acid-resistant reaction vessel, provided with agitator,heating and cooling jacket, and with a reflux condenser. Distillationcondensate did not immediately return to the vessel, but was collectedin a small settling trap, from which condensed liquids couldbewithdrawn, if desired, or returned to the vessel.

The reaction vessel was charged with 500 parts by weight of a mixture ofheterocyclic bases, having a boiling range (bulb distillation) of142.5-145.0 C'. It had approximately the following composition:2,6-lutidine, 28%; 3-picoline, 34%; 4-picoline, 36%; and, in addition,from 0.5 to 1% each of 2-picoline and of 2,4- lutidine. The agitatedbases were gradually mixed with 120 parts by weight of hydrochloric acidof 35% concentration, containing 1.17 molar weight equivalents ofhydrogen chloride as against 1.32 molar equivalents of 2,6-lutidinepresent in the mixture of bases. Sixty parts by weight of toluene wereadded next. The completed charge was heated to refluxing. The condensatewas trapped, allowing itto separate in two layers. The upper layerconsisting of a mixture of toluene and heterocyclic bases wascontinuouslyreturned to the distillation charge,

whereas the lowerwater layer was intermittently withdrawn. The operationwas continued until no appreciable quantity of water separated in thetrap, a total of 82 volume parts of aqueous layer having been collected.

Granular crystals of 2,6-lutidine hydrochloride separated on cooling thecharge to. room temperature. The resulting slurry was centrifuged andthe crystals washed with a small quantity of toluene. Crystals weredried at C., 160 parts of dry material being obtained. The crystalsmelted at 238 C., correctedthe same melting point as determined for thepure compound. They contained parts by weight of. 2,6-lutidine,corresponding to a yield of 82% of the lutidine originally present inthe mixture of bases.

Crystals were dissolved in water and 2,6-lutidine liberated by additionof an aqueous solution containing 45 parts of sodium hydroxide. Theamount of water used in this liberation was so adjusted as to obtain anapproximately saturated solution of sodium chloride. The bulk of theliberated lutidine in that case separates as an upper layer which isdecanted. A small additional quantity of lutidine may be obtained by.partial distillation of the aqueous salt solution. A small quantity ofcondensate containing water and 2,6-lutidine is again saturated withsodium chloride to recover the remainder of the base. The combined yieldof base is completely de-' hydrated and distilled. The material consistsof pure 2,6-lutidine.

The toluene-base mixture recovered as mother liquor from the abovecrystallization was subjected to a further partial precipitation of baseas hydrochlorides in accordance with the process more particularlydescribed in the next example for the purpose of resolving the basespresent into (a) a precipitated hydrochloride fraction greatly enrichedin 4-picoline and (b) a residual frac-v tion of free or uncombined basesgreatly enriched in 3-picoline.

Example 2.--Separation of 2,6-lutidine and 4- Picolz'ne successivelyfrom a B-picoline-Lpic- Zine-Zfi-Zuttdine fraction the remaining 2%consisting of dissolved hydrochlorides of bases and water. A sample ofthe total bases present in this mixture was analyzed and. found tocontain the following components: 2,6-lutidine, 4%; 3-picoline, 52%;4-picoline, 42%. In addition, from 1% to 2% of Z-picoline and2,4-lutidine were present.

The reaction vessel of the preceding example was charged with 1700 partsby weight of the toluene-base mixture just described, and 515 parts byweight of'hydrochloric acid, technical grade, of 32% concentration, wereadded. The charge was heated to refluxing until practically all water,350 parts, had been removed through the trap arrangement. Approximately290 parts by weight of toluene were taken off by fractionaldistillation. The remaining charge was-gradually cooled to roomtemperature; a heavy mass of fineicrysta-ls..consisting,;-predominantlyof A'Pj-COW linezzhydrochloridez separated: out: The-,icrystalwererisolated byz; centriiugi-ngzand;washed-with. toluene :1 recoveredfrom; the: vessel: charge by; fractional distillatiorm Freed :fromrtoluene by drying: these; crystals .tamountedzitosfiooa parts; byWeightr These ;-crystals,: were fairly; hygroscopicand :containedg-aalittle ;ab'sorbed;moistur e:

Bases: wereeisolated drom ethese .crystals by -ad.-; dition'cofaanaqueousasolutiorrioflsodiunr hlVfi-"roXi-v idei The completely dried 1and; distille dz: bases; 4-10: parts sbyzweight; hadcthe .ffo1lowing;:.composi:- tiom. 2;6-1utidine;l 4%; 3=.picoline;. 8% 4%}2100?line;. 88.%.;

Theemotheri liquor obtainedir om 1 the :crystals; combineduwithmtoluene: used irrlwashing ioperae tions, was agitated with a smallquantity 1:so-. dium-hydroxidei solution 0t 30%: concentrationitoneutralize-traces ofi ahydrogerr chloride ndissolttedi in-the:1iquor.:The aqueous. waslrasolutions was drawn ofi 'as a lower layers- The upperlayer; i; e., the washed: toluene," was ifractionally distilled: in: anironstill-until toluene had been taken off. The still residue was thendistilled with ifullzifo'rward fl0w,-665- parts by weight of. basesenriched in: 3-picoline being obtaineds The com-position ofthismaterial' was-"as; follows 2,6-lutidine, 4%; .3- picoline, 76%;4-picoline,-15%. In 'additiomthe. material-- contained -2'-picoline and2,4-lutidinei EazampleiiT-Sleparation of 2,6-lutidine .and,'.4-i

picolzne. simultaneously fr0-m.a 3.-'picoZin e-4- picoline-Zfi-lutidi'nefraction The mixture bases .describediin :the-first: example;1000.:partsnbyi weight; was: charged. in. the reaction, vessel:previously: described-,2 together, with: 80 partsbyweightf:.toluenecands'lw:parts by weight: ofconcentrated: :hydrochloricacidcrof 35%.strength; Waterrwasrremoved-,.by;refi1ixing theicharge.and; with-drawaloi the water: through acseparatingxtrapi.Thepdehydrate'd chargecwas mixed:.lwit-h;380: parts: by weightlof 1amixtureiaofi bases having the following composition: 2,6:-l lutidine,4%; 3-picoline, 74%; 4-picoline, from 1 to 2 jofZ-picolineandZA-lutidine. be= ing present inaddition to the threemain-components.

' The:mixtur ewasagitated. and gradually cooled 1301253 C- A- heavy massoficr-ystals separatedout during the cooling-operation. Crystals czvere3cen triiuged an'd-gwashed with. toluene. to. free-them from motherliquor; Bell-parts by -weight,:. free: of toluene being, obtained. Basesliberated: from the crystals by; customary. procedure amounted to.-656.. ar'ts= by; weight, and had. the-following composition:-2,6+lutidine,;40%-;= .3epicoline, 3.5 5%; i-picolinei 56% .vThe.:motherv liquor obtained from, the crystals; together with toluenesolutions recovered. from; washings operations, .approx.-.imately.1250-parts by weight,;wer.e..wa shed with a; solutioncontaining; 50 rpartsgby weightaotya 30 ..solution;1-ofu sodium.hydroxide. The r-upper layer i. e., the: washed: toluene;; wastfractionallydistilled to remove toluene. 'Ihe-..residual. basesweredistilled with full forward-flow. Including bases, contained in asmall intermediater fraction, aetotal of 701 parts by weightiofiafractionnrich in 3v-picolines. were-thus. obtained-1 hedistilled baseshad the following composition: =2,6=,luti dine, 4 v 3.-.pi.co1ine,, 82.54-.picoline,.= 1,2 traces of Z-picoline and 2,4-lutidine were present.

In a. continuous production, oneshalf. 102? 2 this material. may be.reused .as :a. :diluent. .iniag. subsee quent. .crystallization-.procedure,i.whileetheother halt. is. .withdrawn {as product.Preferably; hows ever, ,runs which result I in r a residual productofhigh 3-picolinercontent, e., 83%85.%-, 3-pico- 1ine,p are, selected:for withdrawalias product; while runsrthat, result in a residual3-picoline 00110911":

tlfitllBrOf lower concentration are; retained separately-foruse asdil-uent in subsequent-runs.

3-picoline concentrates obtained-as inthe aboveexamples-may be workedup. furtherzfor isolation. of pure 3pic01ine;in=the f0rmof-its'phosphate; according to the,- procedure of' my; copending;application Serial No. 3465347. In carrying out such' a process, the3-pico1ine concentrate may; be mixed: with toluene and/with 70%ph0sphoric-acid,: 1, molar equivalent of HsPOr being used-for :every;equivalent of 3-picolineipresent; The mixture is agitated andbroughtitorefluxing to remove all Waterpresent by:azeotropicdistillationandxtrapgpinggofrthelcondensate: Thedehydrated charge;while; still. warm, is diluted with methanol+iand'. cooledito; 20": C.to precipitate 3.-picolinei phosephate; Crystals, produced ;inthis;manner. are coarser :and; more .easily .filterabler The crystahslurry iscentrifuged anctwashed with/methanol at.120" C. The' crystals. are then;dried:.-directly in thecentrifuge. by :blowingwitlr a .blast; of,- airpreheated to about %0; The: 3-picolinexph0sphate crystals.- thusobtained are. dissolved in. water. and .31-picoline liberated byaddition ton-sodium hydroxide. 3=picoline of: 9.7 to: purity may thusbeobtained.

Since-certain changes may. be.-madeincarrying out'the aboveprocesswithout departing fromthezscope of the invention; it is intendedthat all matter contained in the. above description shall beinterpretedas illustrative. and not in' a limiting: sense.

What is=claimed is:

1. A process-for resolving a mixture containing substantial proportionsof. 3-picoline, 4-picoline; and 2 ;6'-lutidine, comprising reacting saidbase mixturewith an amount of hydrogen chlorid just sufficient to reactsubstantially completelvwith' the 2,64lutidineand 4-picoline,- inthe-presence of a diluent selected from the group-rhydrocarbonz solventsand 3-picoline concentrates. to. precip itatev 2:;6I-lutidine and4-picoli'ne from suclrmixture in the form of their hydrochlorides.

2'. In a process for the production of a 3-pico line concentrate :from amixture containing; substan-tial proportions of 2;6.-lutidine,-3.-picoline',. and 4-picoline, the;stepswhichcomprise precipritatinghydrochlorides :of the 2,6-.1utidine and. the 4-.picoliner andseparating the: uncombinedbase; enriched in -3.-picoline; from saidvhyd-rochlorides;

3. In a process -for-the=productioniofsa. 3-picoline concentrate from amixturecontaining sub:- stantial proportions .of 2,6-lutidine,.3pic0line-.and l-picoline; the step s which comprise :reactingasaidbase mixture-with an .amount of hydrogenchlo: ride just sufficient toreact substantially: com-1, pletely=with the 2,6 elutidine and..4.-.picoline,-in the presence 0f3a di1uent:se1ected from the group.hydrocarbon solyentsand- 3- picolineaconcentrates; to: precipitatehydrochlorides of the ..-2,6-lutidine and: theel-picoline;andz-separatinguthe urrconre bined'. base,- enriched-in, 3.-'.picoline;.fronusaid hys; droch'lorides.

4; A: process. for,- the production of. 3-picoline from ar-mixture.of-coaltambases .cOntainingiB picoline; 4-picoline and;2,6-.lutidine;-. which :com-n prises;fractionating'zthebasemixturertorobtain -a cut,:containing substantial.-proportionsiofeaclr'ofz the-above basestreatingthiscut with an amount of hydrogenchloride'justsufiicientv to. react sub-e stantially completely; withthe. 2,6.'lutidine1:and

4-picoline to precipitate hydrochlorides of these bases, and separatingthe precipitated hydrochlorides from the residual uncombined base richin 3-picoline.

5. A process for the production of substantially pure 3-pico1ine from amixture of coal tar bases containing B-picoline, 4-picoline and2,6-1utidine, which comprises fractionating the base mixture to obtain acut boiling predominantly in the range of about 140 to 145 C. andcontaining substantial proportions of each of the above bases, treatingthis cut, in the substantial absence of water, methanol and ethanol,with an amount of hydrogen chloride just sufficient to reactsubstantially completely with the 2,6-lutidine and 4-picoline toprecipitate hydrochlorides of these bases, separating the precipitatedhydrochlorides from the residual uncombined base rich in 3-picoline andisolating substantially pure 3-picoline,;from said residual base in theform of its phosphate.

6. In a process for resolving a mixture containing substantialproportions of 3-picoline, 4-picoline, and 2,6-1utidine, the steps whichcomprise treating the base mixture with an amount of hydrogen chloridesufficient to react with the major part but not all of the 2,6-lutidineto precipitate substantially pure 2,6-lutidine from such mixture in theform of its hydrochloride, separating the precipitate thus formed,treating the residual uncombined base mixture with an amount of hydrogenchloride substantially equivalent to the 4-picoline and 2,6-lutidineremaining in said base mixture to precipitate these bases from themixture in the form of their hydrochlorides, and separating theprecipitate thus formed from the uncombined base rich in 3-picoline.

'7. In a process for resolving a mixture containing substantialproportions of 3-picoline, 4-picoline, and 2,6-lutidine, the steps whichcomprise treating the base mixture with an amount of hydrogen chloridesufficient to react with the major part but not all of the 2,6-1utidineto precipitate substantially pure 2,6-1utidine from such mixture in theform of its hydrochloride, separating the precipitate thus formed andconverting it to free base by treatment with alkali, treating theresidual uncombined base mixture with an amount of hydrogen chloridesubstantially equivalent to the 4-picoline and 2,6-lutidine remaining insaid base mixture to precipitate these bases from the mixture in theform of their hydrochlorides, separating the precipitate thus formedfrom the uncombined base rich in 3-picoline, converting the separatedhydrochloride precipitate to free base by treatment with alkali, andtreating the uncombined base rich in 3-picoline to separatesubstantially pure 3-picoline therefrom in the form of its phosphate.

8. A process for resolving into its components a nitrogen base mixturecomprising 3-pico1ine and 4-pico1ine which comprises reacting saidmixture with hydrogen chloride and forming a reaction mixture containingsubstantially no water and lower alcohols, whereby 4-picolinehydrochloride is precipitated preferentially to 3-picolinehydrochloride.

9. A process for resolving into its components a nitrogen base mixturecomprising 2,6-1utidine and at least one of the bases 3-picoline and 4-picoline which comprises reacting said mixture with hydrogen chlorideand forming a reaction mixture containing substantially no water andlower alcohols, whereby 2,6-lutidine hydrochloride is precipitatedpreferentially to picoline hydrochloride.

10. A process for resolving into its components a nitrogen base mixturecontaining at least two of the bases 2,6-lutidine, 4-picoline andB-picoline which comprises reacting said mixture with hydrogen chlorideand forming a reaction mixture containing substantially no water andlower alcohols, whereby the hydrochloride of at least one of theindividual bases in said mixture is precipitated, the order ofpreference for precipitation of individual base hydrochlorides being theorder in which the bases are above named.

11. In a process for the production of a 3-picoline concentrate from amixture containing substantial proportions of 2,6-lutidine, 3-picolineand l-picoline, the steps which comprise reacting said base mixture withan amount of hydrogen chloride just sufficient to react substantiallycompletely with the 2,6-lutidine and 4-Picoline, in the presence of ahydrocarbon diluent, to precipitate hydrochlorides of the 2,6-lutidineand the 4-picoline, and separating the uncombined base, enriched inS-picoline, from said hydrochlorides.

KARL HENRY ENGEL.

REFERENCES CITED The following references are of record in the.

file of this patent:

UNITED STATES PATENTS Number Name Date 2,288,281 Huijser June 30, 19421,965,828 Fox July 10, 1934 2,035,583 Bailey Mar. 31, 1936 2,035,584Bailey Mar. 31, 1936 FOREIGN PATENTS Number Country Date 570,675 Germany1933 OTHER REFERENCES Maier, Das Pyridin and Seine Derivative (1934)page 30. (Copy in Div. 59.)

Journal of Chem. Society of London 1940, pp. 241-3.

Journal of Chem. Society of London, vol. 95, 1909, pp. 668-85.

